2012-2013年北京市大气PM2.5污染成分分析

摘要

选取北京市近郊区5个不同功能定位的采样点,采用重量法仪器,采集2012年8月—2013年7月的PM2.5环境受体样品,共获取1200余张滤膜样品,分析颗粒物质量浓度状况和地域间以及季节分布规律,并分析了水溶性离子、有机碳/元素碳等组分.结果表明,北京市全年 ρ(PM2.5)范围在19.27~894.23μg·m-3之间,日平均 ρ(PM2.5)为126.38μg·m-3,污染水平较高;北京市PM2.5质量浓度以冬季最高,为207.8μg·m-3;工业区质量浓度较高但与城区差距不明显,房山和亦庄两个工业区平均 ρ(PM2.5)为155.4μg·m-3,而城区的东四 ρ(PM2.5)则达到了124.2μg·m-3.有机碳是PM2.5中含量最高的组分,且与元素碳来源基本一致,有机碳的质量浓度范围为3.84~164.1μg·m-3,平均质量浓度21.43μg·m-3;元素碳的质量范围为0.53~22.07μg·m-3,平均质量浓度3.53μg·m-3,两者质量浓度相对于国内其他主要城市处于较高水平;OC和EC冬季来源较为明显,为燃煤污染;二次有机碳质量浓度在冬季和工业区相对较高.硝酸盐为水溶性离子中含量最高的组分,主要来自于燃煤锅炉排放和机动车尾气污染;无机金属元素以硅与钙为主,地面扬尘及建筑工地也是PM2.5的重要来源.%1200 groups of PM2.5 samples were collected from August 2012 to July 2013 by filter membrane weighting method in five sites from different locations in suburban areas of Beijing. The mass concentration, regional and seasonal distribution, as well as chemical characteristics of PM2.5, namely water-soluble ions, organic carbon (OC) and elemental carbon (EC), were analyzed. The results indicated that the PM2.5 concentrations were high, which were in the range of 19.27~894.23 μg?m-3 with daily average con-centration of 126.38 μg?m-3. The PM2.5 concentration was higher in winter (207.8 μg?m-3) than in other seasons. The PM2.5 concentra-tion in industrial area was higher than that in urban area, but the disparity was insignificant. The average mass concentration of PM2.5 in industrial areas (Fangshan and Yizhuang) was 155.4 μg?m-3, which was about 25% higher than that in urban area with an average mass concentration of 124.2 μg?m-3. The sources of OC were consistent with those of EC, and the OC had the highest proportion in PM2.5 compared with other components. The mass concentrations of OC and EC in PM2.5 from Beijing were at high level compared to those measured in other cities. The mass concentrations of OC in PM2.5 were in the range of 3.84~164.1 μg?m-3 with an average concentration of 21.43 μg?m-3; while those of EC in PM2.5 were 3.53 μg?m-3 which were in the range of 0.53~22.07 μg?m-3. The EC and OC mainly came from coal burning in winter. The mass of secondary organic carbon (SOC) was relatively high in winter and in industrial area. Nitrate, which mainly came from coal-fired boilers and vehicles, had the highest concentration among the wa-ter-soluble ions. The silicon and calcium was the principal inorganic metallic elements, indicating the construction sites and uncov-ered lands were the main sources of PM2.5 in Beijing.